Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: various instrumentation and parts questions
Date: Jul 06, 6:16 pm
Poster: Jim Lux

On Jul 06, 6:16 pm, Jim Lux wrote:

> Ok, I'm looking to go to 30 kV grid voltage (the x-ray supply I'm looking at can hit 125 kV, but will be limited to 30 kV). Do you know if
sparkplugs will handle this kind of voltage?

Yes, at least in air.. The creepage path is quite long on most spark plugs, and that is what will determine the breakdown. Richard's comment about good silicone boots is important though. 30 kV is high enough where corona is a significant problem in air. Watch your conductor diameters and radii of curvature on connections, nuts, bolts, and the like.

> Don't I know it! I was just looking at the weld lip ones, and suffering some serious sticker shock.

Standard bolt in BNC hermetic are about $7 from places like Pasternak Enterprises. You might be able to use a vanilla panel mount BNC ($1-$2) and glop the back side up with sealant after soldering the coax on. Should be good up to 100 MHz without any real problems.
Bulkhead N Females with pressure seals (but not hermetic) are around $5

If you need more oomph (like MHV and the like, the hermetic parts run around $20)
>>How good of an impedance match do you need, or are you just concerned about shielding?
> Doesn't have to be perfect, but it would be nice if it was known, so I could build a matching network if necessary.

I don't know that I'd try to match the discontinuity from the connector. How broadband is your signal?